Abstract
A new species of the mainly terrestrial enchytraeid oligochaete genus Achaeta is described from 'terra firme' soils of the Amazonian primary rain forest near Manaus, Brazil. Achaeta becki sp. nov. is about 6 mm long; its main distinguishing characters are a very short vas deferens, thickened septa in almost all segments, and a dorsal blood vessel origin in the clitellar region. Oesophageal appendages, pyriform glands (=setal follicles), and secondary pharyngeal gland lobes are absent. Further distinguishing characters are: pharyngeal glands separate in VI, extending into VII, preclitellar nephridia at 6/7 and 8/9, spermathecal ectal pores lateral. The new species is most similar to A. maorica Benham, 1903, A. neotropica Ñernosvitov, 1937, and A. iridescens Christoffersen, 1979, all from the southern hemisphere. Similarities and differences are discussed in detail.
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